MORBID ANATOMY OF LEAD PARALYSIS 227 
efferent nerves, the fibres in the muscle spindle which are derived from the posterior roots being 
throughout normal. As regards the condition of the spinal cord, the introduction of a more 
delicate method of staining has made it possible to detect more minute structural changes than the 
older methods were capable of demonstrating. It has now been amply shown that many poisons, 
and among metals notably those of arsenic, antimony, and lead, when administered to animals, 
produce fairly constantly changes in the nerve cells. Nissl* and ScHAFERt have studied the 
changes produced by the administration of lead and practically agree in their description of the 
altered cells when stained by the methylene blue method. 
The process consists essentially in a disintegration and dispersion of the chromatic bodies 
and shrinking of the nucleus ; in more advanced conditions a chromatolysis sets in so that 
ultimately a mere palely-stained shell-like mass represents the cell. 
Such changes probably are due to the direct action of the lead on the central nervous system, 
but with the existence of multiple neuritis a second factor has to be considered in explaining any 
alteration of the cells of the spinal cord. After the work of Nissl and others it may be accepted 
that loss of continuity of the axon is followed at an early period by changes in the corresponding 
cell. Such changes have been shown by one of usj to be especially pronounced after division of 
an anterior root. 
Hence in the above case, where the anterior roots of Vlth and Vllth segments show some 
markedly atrophied fibres, it has to be considered whether the changes in the spinal cord are the 
result of the direct action of the poison, or if, on the other hand, they are secondary to a lesion of 
the axis cylinder producing the ' reaction a distance ' of Marinesco.§ This observer indeed 
maintains that the histological features presented by the nerve cell are in general cliaracteristic of 
a * primary ' or ' secondary ' lesion. || A study of the changes in structure occurring in nerve 
cells in various pathological conditions does not lead us to believe that the histological features 
alone offer distinctive evidence of their origin. Nevertheless, the condition of the nerve cells in 
which, together with chromatolysis, the nucleus is eccentric, is rarely found except as a consequence 
of an interference with the afferent or efferent impulses. 
This, combined with the fact that in our case the altered cells are almost absent from the 
IVth and Vth segments but found in the Vlth and Vllth segments, the anterior root fibres of 
which show some atrophy and from which the much atrophied posterior interosseous nerve is 
derived, points distinctly to the inference that the changes described in the spinal cord are the result 
not of the direct action of the lead, but as a consequence of the altered state of functional activity 
following atrophy of the axons of these cells. In cases of polyneuritis from other causes 
MarinescoH and Ballet** have recorded similar changes in the nerve cells of the spinal cord 
wliich they regard as being due to this cause. These facts, combined witli the experimental 
evidence, indicate that a more extended view must be taken of the pathology of multiple neuritis. 
* Nissl, 'All. Zeitschr. f. Psych.,' Bel. 48, p. 675. 
t Sch'afer, ' Neurol. Central.,' pp. 148 anri 900, 1894. 
J Warrington, loc. cit, 
§ Marinesco, ' Revue Neurologique,' March 15, 1896. 
II ' Comptes Rendus de la Societe de Biologic,' January 25, 1896. 
f\ Ihui. 
** Le ' Progres Medical,' June 27, 1896. 
